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(11) | EP 2 251 531 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
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FUEL INJECTION CONTROL DEVICE STEUERVORRICHTUNG FÜR KRAFTSTOFFEINSPRITZUNG DISPOSITIF DE COMMANDE D'INJECTION DE CARBURANT |
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| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
TECHNICAL FIELD
[0001] The present invention relates to a fuel injection control device provided with a injector for cylinder outside injection that injects fuel into an exhaust passage of an engine.
BACKGROUND ART
[0002] The exhaust gas discharged by a diesel engine contains, for instance, particulate matter (PM) and nitrogen oxides (NOx). There are methods in which a filter (diesel particulate filter) having a catalyst or the like is provided in an exhaust passage of an engine, in order to capture PM in the exhaust gas, and fuel is injected into the exhaust passage, upstream of the filter, in order to remove the PM captured by the filter (see Patent Documents 1 and 2).
[0003] Means for injecting fuel into an exhaust passage include, for instance, injectors for low-pressure injection (for instance, multihole nozzles and swirl nozzles for gasoline engines). In driving control of such injectors for low-pressure injection, an actuator that drives the injector is driven at a constant driving frequency (for instance, 100 Hz). The amount of fuel injected by the injector is controlled by changing a duty ratio that is determined on the basis of the driving frequency.
[0004] The initial stage of valve opening in the injector comprises a so-called dead time period (duty ratio of about 0 to 10%) in which a needle valve (needle) is not lifted, and no fuel is injected. The last stage of valve opening includes a so-called stable time period (duty ratio 90% or higher) in which the needle valve is substantially not closed. Therefore, the injector is used within a duty ratio range of about 10 to 90%, by avoiding the dead time and stable time (see injection amount characteristics in Fig. 5 (with pressurization)).
[0005]
Patent Document 1: Japanese Patent Application Laid-open No. 2002-295298
Patent Document 2: Japanese Patent Application Laid-open No. 2007-315313
[0006] JP 2004 108344 A discloses a fuel injection control device according to the preamble of claim 1. In particular, this Document discloses a burner supplying burnt or ignited HC when the exhaust temperature is equal to or lower than a threshold temperature, while the burner supplies unburnt HC when the exhaust temperature is higher than the threshold temperature. A duty ratio between a period during which unburnt HC is supplied and a period during which burnt HC is supplied as well as a cycle time are determined on the basis of the exhaust temperature. As the exhaust temperature increases, the duty ratio is increased, and the cycle time is decreased.
[0007] The post-published Document WO 2008/045499 A2 discloses a dual injector system comprising a first injector as a lead injector and a second injector as a lack injector. The frequency of the first injector is changed in accordance with the engine load.
DISCLOSURE OF THE INVENTION
PROBLEMS TO BE SOLVED BY THE INVENTION
[0008] When using the above-described injector for low-pressure injection as a means for injecting fuel into an exhaust passage, the atmosphere pressure inside the exhaust passage (outside the cylinder) is lower than inside the combustion chamber (inside the cylinder). As a result, the set pressure of the needle valve can be made lower than is the case when the injector is used for in-cylinder injection, and it becomes possible also to use a driving driver without fuel pressurization. Therefore, using the above-described injector for low-pressure injection as a means for injecting fuel into an exhaust passage allows reducing costs, by omitting a pressurization circuit that raises the pressure of fuel that is fed to the injector.
[0009] However, omitting the pressurization circuit tends to result in a protracted dead time owing to the resulting drop in driving torque. This gives rise to variability in the amount of injection by the injector when the injection amount is small, and causes the lower limit range of the injection amount by the injector to increase as compared with a case where the fuel is pressurized (injection amount characteristic of Fig. 5 (without pressurization)).
[0010] Therefore, it is an object of the present invention to provide a fuel injection control device that affords a wider lower limit range of injection amount by a injector for cylinder outside injection, and that can respond to injection requirements over a wider injection amount range.
MEANS FOR SOLVING THE PROBLEMS
[0011] In order to attain the above goal, the present invention provides a fuel injection control device according to claim 1.
EFFECT OF THE INVENTION
[0012] The present invention affords the advantageous effect of providing a fuel injection control device that affords a wider lower limit range of injection amount by a injector for cylinder outside injection, and that can respond to injection requirements over a wider injection amount range.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013]
Fig. 1 is a schematic diagram of a fuel injection control device according to an embodiment of the present invention;
Fig. 2 is a diagram illustrating a process flow by an ECU;
Fig. 3 is a diagram illustrating schematically a table in which there is inputted driving frequency mapped to required injection amount;
Fig. 4(a) and Fig. 4(b) are diagrams illustrating duty ratios; and
Fig. 5 is a diagram illustrating an injection amount characteristic of an injector.
DESCRIPTION OF THE REFERENCE NUMERALS
[0014]
1 engine (diesel engine)
12 exhaust passage (exhaust pipe)
14 out-cylinder injector (injector for cylinder outside injection)
15 ECU (control means)
BEST MODE FOR CARRYING OUT THE INVENTION
[0015] A preferred embodiment of the present invention is explained in detail below with reference to accompanying drawings.
[0016] As illustrated in Fig. 1, an engine 1 (in the present embodiment, a diesel engine) comprises, for instance, a cylinder 2, a cylinder head 3, a piston 4, an intake port 5, an exhaust port 6, an intake valve 7, an exhaust valve 8 and an in-cylinder injector (injector for cylinder inside injection) 9. A combustion chamber 10 is formed in the space delimited by the cylinder 2, the cylinder head 3 and the piston 4. Fuel is injected directly from the in-cylinder injector 9 into the combustion chamber 10. An intake passage (intake pipe) 11 is connected to the intake port 5. An exhaust passage (exhaust pipe) 12 is connected to the exhaust port 6.
[0017] The fuel injection control device according to the present embodiment is used as an exhaust purification device of the engine.
[0018] Such a fuel injection control device comprises a filter (diesel particulate filter) 13, provided in the exhaust passage 12 of the engine 1, that captures particulate matter (PM) present in exhaust gas; an out-cylinder injector (injector for cylinder outside injection) 14 provided upstream of the filter 13 in the exhaust passage 12, and which injects fuel into the exhaust passage 12, in order to remove the PM captured by the filter 13; and a control means (hereafter, ECU) 15 that controls the out-cylinder injector 14.
[0020] The ECU 15 estimates the amount of PM captured by the filter 13 on the basis of, for instance, a pressure ratio or differential pressure that is measured by exhaust gas pressure sensors 16, 17 that are provided upstream and downstream, respectively, of the filter 13. When the estimated amount of captured PM exceeds a predetermined amount, and the exhaust gas temperature measured by an exhaust gas temperature sensor 18 that is provided upstream of the filter 13 is lower than a predetermined temperature, the ECU 15 carries out exhaust pipe injection, in which the out-cylinder injector 14 injects fuel into the exhaust passage 12 in order to raise the temperature of the exhaust gas to a predetermined temperature or higher.
[0021] The fuel injection amount by the out-cylinder injector 14 is controlled through changes in a duty ratio that is determined on the basis of the driving frequency of the out-cylinder injector 14.
[0022] The ECU 15 changes the driving frequency of the out-cylinder injector 14 (actuator) in such a manner that the frequency becomes continuously lower as the required injection amount decreases (see Fig. 3).
[0023] In the present embodiment, the ECU 15 sets the driving frequency of the out-cylinder injector 14 (actuator) to a high frequency (for instance, 100 Hz) when the required injection amount is largest (see Fig. 4(a)), sets the driving frequency of the out-cylinder injector 14 (actuator) to a low frequency (for instance, 15 Hz) when the required injection amount is smallest (Fig. 4(b)), and changes continuously the driving frequency of the out-cylinder injector 14 (actuator) from the high frequency (100 Hz) to the low frequency (15 Hz) as the required injection amount decreases (see Fig. 3).
[0025] When there is an injection request for the out-cylinder injector 14 (S1 in Fig. 2), the ECU 15 selects a driving frequency corresponding to the required injection amount, on the basis of a table in which driving frequency is inputted beforehand mapped to required injection amount (S2 in Fig. 2).
[0026] The ECU 15 calculates next a duty ratio on the basis of the driving frequency, selected from the table, that corresponds to the required injection amount, and determines whether the calculated duty ratio (designated duty) is a value lying between a predetermined lower limit duty and a predetermined upper limit duty (lower limit duty < designated duty < upper limit duty) (S3 in Fig. 2).
[0027] If the designated duty is a value lying between a predetermined lower limit duty and a predetermined upper limit duty, the ECU 15 drives the out-cylinder injector 14 (actuator) in accordance with the designated duty, to elicit thereby injection into the exhaust pipe by the out-cylinder injector 14 (S4 in Fig. 2).
[0028] When in the present embodiment the required injection amount is smallest, there is selected, as the driving frequency of the out-cylinder injector 14 (actuator), a frequency (15 Hz) that is lower than the frequency when the required injection amount is large. As a result, the lower limit of the injection amount by the out-cylinder injector 14 is 0.15 times (15/100 = 1/6.7 times) the injection amount at the time where the driving frequency is constant (100 Hz), assuming that the injection pressure of the fuel remains the same.
[0029] That is, the injector can be used down to a low injection amount range, and the lower limit range of the injection amount by the out-cylinder injector 14 can be expanded, by enabling the driving frequency of the out-cylinder injector 14 (actuator) to be changed to a frequency lower than 100 Hz, as compared with a case (see Fig. 3) in which the driving frequency of the out-cylinder injector 14 (actuator) is constant (100 Hz).
[0030] When in the present embodiment the required injection amount is greatest, there is selected, as the driving frequency of the out-cylinder injector 14 (actuator), a frequency (100 Hz) that is higher that the frequency when the required injection amount is small. As a result, the upper limit of the injection amount by the out-cylinder injector 14 is the same injection amount as the injection amount when the driving frequency is constant (100 Hz), assuming that the injection pressure of the fuel remains the same.
an injector (14) for cylinder outside injection for injecting fuel into an exhaust passage (12) of an engine (1), in an amount corresponding to a duty ratio; and
control means (15) adapted for controlling the injector (14) for cylinder outside injection,
characterized in that the control means is adapted to change an injector driving frequency upon determining the duty ratio from a high frequency when the required injection amount is largest to a low frequency when the required injection amount is smallest, such that the frequency is lowered continuously, as the required injection amount decreases,
wherein the control means (15) is adapted to select the injector driving frequency corresponding to the required injection amount on the basis of a table in which the driving frequency is inputted beforehand mapped to the required injection amount, to calculate the duty ratio on the basis of the selected injector driving frequency, and to drive the injector (14) for cylinder outside injection in accordance with the calculated duty ratio when the calculated duty ratio is a value lying between a predetermined lower limit duty and a predetermined upper limit duty.
wherein the control means is adapted to set the injector driving frequency to 100 Hz when the required injection amount is largest, to set the injector driving frequency to 15 Hz when the required injection amount is smallest, and to change continuously the injector driving frequency from 100 Hz as the high frequency to 15 Hz as the low frequency as the required injection amount decreases.
wherein the lower limit duty is 10%, and the upper limit duty is 90%.
wherein the control means (15) is adapted not to carry out cylinder outside injection when the calculated duty ratio is not a value lying between the lower limit duty and the upper limit duty.
einen für eine Einspritzung außerhalb eines Zylinders vorgesehenen Einspritzer (14) zum Einspritzen von Kraftstoff in einen Abgaskanal (12) eines Motors (1) in einer einem Tastverhältnis entsprechenden Menge, und
Steuermittel (15), die angepasst sind, den für eine Einspritzung außerhalb eines Zylinders vorgesehenen Einspritzer (14) zu steuern,
dadurch gekennzeichnet, dass das Steuermittel angepasst ist, eine Einspritzeransteuerfrequenz mit Bestimmen des Tastverhältnisses von einer hohen Frequenz, bei der die erforderliche Einspritzmenge am größten ist, in eine niedrige Frequenz, bei der die erforderliche Einspritzmenge am kleinsten ist, so zu ändern, dass die Frequenz mit Abnahme der erforderlichen Einspritzmenge kontinuierlich verringert wird,
wobei das Steuermittel (15) angepasst ist, die der erforderlichen Einspritzmenge entsprechende Einspritzeransteuerfrequenz auf Grundlage einer Tabelle zu wählen, in der die Ansteuerfrequenz im Voraus in Zuordnung zu der erforderlichen Einspritzmenge eingegeben worden ist,
das Tastverhältnis auf Grundlage der gewählten Einspritzeransteuerfrequenz zu berechnen,
und den für eine Einspritzung außerhalb eines Zylinders vorgesehenen Einspritzer (14) gemäß dem berechneten Tastverhältnis anzusteuern, wenn das
berechnete Tastverhältnis ein Wert ist, der zwischen einem vorbestimmten unteren Grenztastverhältnis und einem vorbestimmten oberen Grenztastverhältnis liegt.
wobei das Steuermittel angepasst ist, die Einspritzeransteuerfrequenz auf 100 Hz einzustellen, wenn die erforderliche Einspritzmenge am größten ist,
ein Einspritzeransteuerfrequenz auf 15 Hz einzustellen, wenn die erforderliche Einspritzmenge am kleinsten ist, und
die Einspritzeransteuerfrequenz kontinuierlich von 100 Hz als höchste Frequenz auf 500 Hz als niedrigste Frequenz zu ändern, wenn die erforderliche Einspritzmenge abnimmt.
wobei das untere Grenztastverhältnis 10% und das obere Grenztastverhältnis 90% ist.
wobei das Steuermittel (15) angepasst ist, eine Einspritzung außerhalb eines Zylinders nicht durchzuführen, wenn das berechnete Tastverhältnis nicht ein Wert ist, der zwischen dem unteren Grenztastverhältnis und dem oberen Grenztastverhältnis liegt.
un injecteur (14) pour injection à l'extérieur du cylindre permettant d'injecter du carburant dans un passage d'échappement (12) d'un moteur (1), en une quantité correspondant à un rapport de cycle ; et
un moyen de commande (15) conçu pour commander l'injecteur (14) pour injection à l'extérieur du cylindre,
caractérisé en ce que le moyen de commande est conçu pour changer une fréquence de commande d'injecteur au moment de la détermination du rapport de cycle, entre une fréquence élevée lorsque la quantité d'injection nécessaire est la plus importante et une fréquence basse lorsque la quantité d'injection nécessaire est la moins importante, de telle sorte que la fréquence diminue de façon continue au fur et à mesure que la quantité d'injection nécessaire diminue,
dans lequel le moyen de commande (15) est conçu pour sélectionner la fréquence de commande d'injecteur correspondant à la quantité d'injection nécessaire en se fondant sur un tableau dans lequel la fréquence de commande est entrée préalablement appliquée à la quantité d'injection nécessaire, pour calculer le rapport de cycle en se fondant sur la fréquence de commande d'injecteur sélectionnée, et pour commander l'injecteur (14) pour injection à l'extérieur du cylindre en fonction du rapport de cycle calculé lorsque le rapport de cycle calculé est une valeur comprise entre un rapport de cycle de limite inférieure prédéterminé et un rapport de cycle de limite supérieure prédéterminé.
dans lequel le moyen de commande est conçu pour définir la fréquence de commande d'injecteur à 100 Hz lorsque la quantité d'injection nécessaire est la plus importante, pour définir la fréquence de commande d'injecteur à 15 Hz lorsque la quantité d'injection nécessaire est la moins importante, et pour changer en continu la fréquence de commande d'injecteur entre 100 Hz, comme haute fréquence et 15 Hz comme basse fréquence au fur et à mesure que la quantité d'injection nécessaire diminue.
dans lequel le rapport de cycle de limite inférieure est 10 %, et le rapport de cycle de limite supérieure est 90 %.
dans lequel le moyen de commande (15) est conçu pour ne pas effectuer d'injection à l'extérieur du cylindre lorsque le rapport de cycle calculé n'est pas une valeur comprise entre le rapport de cycle de limite inférieure et le rapport de cycle de limite supérieure.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.
Patent documents cited in the description